diff --git a/widget/gtk/ScreenHelperGTK.cpp b/widget/gtk/ScreenHelperGTK.cpp
--- a/widget/gtk/ScreenHelperGTK.cpp
+++ b/widget/gtk/ScreenHelperGTK.cpp
@@ -260,18 +260,25 @@
   gint heightMM = gdk_screen_get_monitor_height_mm(aScreen, aMonitorNum);
   if (heightMM > 0) {
     dpi = rect.height / (heightMM / MM_PER_INCH_FLOAT);
   }
 
+  bool isHDR = false;
+#ifdef MOZ_WAYLAND
+  if (GdkIsWaylandDisplay()) {
+    isHDR = WaylandDisplayGet()->IsHDREnabled();
+  }
+#endif
+
   LOG_SCREEN(
       "New monitor %d size [%d,%d -> %d x %d] depth %d scale %f CssScale %f  "
-      "DPI %f refresh %d ]",
+      "DPI %f refresh %d HDR %d]",
       aMonitorNum, rect.x, rect.y, rect.width, rect.height, pixelDepth,
-      contentsScale.scale, defaultCssScale.scale, dpi, refreshRate);
-  return MakeAndAddRef<Screen>(rect, availRect, pixelDepth, pixelDepth,
-                               refreshRate, contentsScale, defaultCssScale, dpi,
-                               Screen::IsPseudoDisplay::No, Screen::IsHDR::No);
+      contentsScale.scale, defaultCssScale.scale, dpi, refreshRate, isHDR);
+  return MakeAndAddRef<Screen>(
+      rect, availRect, pixelDepth, pixelDepth, refreshRate, contentsScale,
+      defaultCssScale, dpi, Screen::IsPseudoDisplay::No, Screen::IsHDR(isHDR));
 }
 
 void ScreenGetterGtk::RefreshScreens() {
   LOG_SCREEN("ScreenGetterGtk::RefreshScreens()");
   AutoTArray<RefPtr<Screen>, 4> screenList;
@@ -286,10 +293,11 @@
 
   ScreenManager::Refresh(std::move(screenList));
 }
 
 gint ScreenHelperGTK::GetGTKMonitorScaleFactor(gint aMonitorNum) {
+  MOZ_ASSERT(NS_IsMainThread());
   GdkScreen* screen = gdk_screen_get_default();
   return aMonitorNum < gdk_screen_get_n_monitors(screen)
              ? gdk_screen_get_monitor_scale_factor(screen, aMonitorNum)
              : 1;
 }